This invention relates in general to fiber optic switches and, more specifically, to a novel light cone switch for use in remote switching systems using a single fiber or a thin bundle of fibers to carry the switching signal.
Conventionally, switches having at least two insulated metal wires are used to connect switches to electrical devices, such as lights, motors, fans, heaters or the like, to allow the device to be turned on and off.
Use of conventional electrical wiring and electrical switches can be hazardous in a number of environments. For example, around swimming pools, spas, whirlpool tubs and the like, where the users are immersed in water and may operate electrical switches with wet hands a serious shock or electrocution hazzrd can exist. Also, corrosion and rusting of the switches and wiring is likely.
Electrical wiring and switches are also subject to corrosion problems when used on boats or in other marine applications. Further, electromagnetic interference may be produced by the operation of radar units and other electronic devices interacting with electrical wiring and electrical switches.
In hazardous or explosive environments, such as oil refineries, natural gas plants, grain elevators, mines, etc., electrical switches and wiring may produce sparks causing fires or explosions. Further, electrical switches designed for use in wet or hazardous environments tend to be expensive, heavy and bulky resulting in large, expensive control panels and the like. Electrical cables often require heavy insulation and shielding in such environments, making installation costly and difficult.
In new building construction, electrical wires are extended through walls, requiring cutting holes through studs, and threading the wires therethrough. There is always a danger that someone, during construction or later, may insert screws or nails into the wall, drill holes, etc. and contact the wires, resulting in electrical shock and fire hazards.
In remodeling of rooms or adding new electrical devices, adding switches with insulated metal wires between the new switches and devices is expensive and difficult, requiring fishing wires through holes in studs behind existing, covered, walls. In some cases, switches are desired on thin partition walls or solid masonry walls where the wiring cannot be hidden. The use of surface mounted wires or loose extension cords is both visually undesirable and a safety hazard.
Recently, a number of small hand-held remote controls using a radio frequency or infrared signal sent to a receiver at the device to be controlled have been developed. These are very effective in a number of applications, such as the control of audio or video entertainment equipment. They are, however, less successful in applications such as the control of room lights and similar permanent devices. These remote controls require batteries that must be replaced periodically and they cannot be allowed to get wet and often cannot be used in hazardous environments.
In an effort to overcome these problems with remote electrical switches using metal, current carrying, wiring, the use of fiber optics has been proposed. Speers, in U.S. Pat. No. 4,023,887 discloses complex switching systems using cables each made up of a plurality of parallel optical fibers to carry various signals. While these cables may be laminated to walls, it is apparent that the size of the cables will result in obvious, obtrusive strips across the wall, since at least two optical fibers are needed between each switch and controlled device. Similarly, Matsunaga et al, in U.S. Pat. No. 4,705,348 discloses an optical switch using two optical fibers between a complex switch and the device being controlled. The reflector used by Matsunaga et al would require very precise alignment of the fiber ends and the reflector and careful orientation and polishing of the fiber ends to be certain that sufficient light entering from one fiber is reflected into the other.
Others, such as Narondy in U.S. Pat. No. 3,886,544 and Ho et al in U.S. Pat. No. 4,797,549 describe systems which simply interpose a blocking or reflecting member into a break between two coaxial optical fibers to selectively block or permit light passage. These techniques require highly polished fiber ends, cut precisely 90.degree. to the fiber axis and careful alignment of the fiber ends to allow sufficient transfer of light from one fiber to the other.
In U.S. Pat. No. 5,163,112, assigned to the assignee of this application, is described an improved remote switch system using a single optical fiber, or a very thin optical fiber bundle, running between an electrical device to be controlled and a remote location. A light emitter and a light detector are located at the device end of the fiber and a movable retro reflector is located at the remote location. A pulse of light could be sent to the device by rotating the retro reflector from a position out of alignment with the fiber end, through an aligned position that would reflect light back into the fiber to a second out of alignment position. While highly effective, this optical switching system requires means for rotating the retro reflector into and out of position at the end of the fiber. Also, this system is not capable of gradually varying the light level sent back through the fiber.
Thus, there is a continuing need for improved switches and switching systems for switching light signals in fiber optic systems to switch various devices between states, that can be safely used in wet, corrosive or hazardous environments and that have greater reliability, compactness and simplicity than prior non-wired systems.